1. Field of the Invention
The present invention relates to a device incorporated in the exhaust system of an automotive or similar internal combustion engine for purifying exhaust gases emanating from the engine and, more particularly, to an exhaust purifying device of the type using a metallic core having a honeycomb structure and coated with a catalyst.
2. Description of the Related Art
An exhaust purifying device or so-called catalytic converter has customarily been incorporated in the exhaust system of an automotive or similar internal combustion engine, e.g., an exhaust pipe or a muffler. Provided with a catalyst, the catalytic converter promotes the oxidation of carbon monoxide, hydrocarbons and other toxic components contained in exhaust gases emanating from the engine. One of conventional catalytic converters has a cylindrical casing attached to predetermined part of, for example, a muffler, and a metallic honeycomb core received in the casing and coated with a catalyst. The honeycomb core is made up of a corrugated sheet of metal and a flat sheet of metal which are rolled up together in a spiral configuration. Such a core is inserted into the casing and then soldered together with the casing. As a result, the corrugated sheet and flat sheet are bonded together to prevent the honeycomb structure from being deformed while, at the same time, the outer periphery of the core is bonded to the inner periphery of the casing to prevent the core from moving in the casing. However, the problem with this kind of catalytic converter is that the soldering operation is complicated and time-consuming. This, coupled with the fact that the solder itself is expensive, increases the cost of the catalytic converter.
To eliminate the above problem particular to soldering, Japanese Patent Laid-Open Publication No. 94015/1988, for example, discloses an exhaust purifying device in which a core is received in a cylindrical casing, but the former is not soldered to the latter. Specifically, retaining members are each affixed to one end of the casing in such a manner as to extend through the center of the opening of the casing. The retaining members prevent the core from slipping out of the casing and prevent the radially central portion of the core from protruding from the casing in an auger-like configuration. On the other hand, U.K. Patent 1452982 teaches an exhaust purifying device having similar support members affixed to opposite ends of a casing.
However, the conventional retaining members or support members affixed to the cylindrical casing as stated above simply restrict the core in the axial direction of the casing, i.e., they cannot cope with the movement of the core in the circumferential direction. As a result, when an automotive vehicle with such an exhaust purifying device is in travel, the core is apt to move in the circumferential direction within the casing due to the stream and heat of engine exhaust, vibration of the vehicle body and so forth. Specifically, it is likely that the core rotates within the casing while the corrugated sheet and flat sheet shift and rub against each other within the core. This would cause the catalyst to come off the core while cracking or breaking the core itself, degrading the expected function of the device.